Process for coloring aqueous emulsions of resins



Patented Aug. 29,1950

! PROCESS FOR COLORING AQUEOUS EMULSIONS F RESINS Harold F. Park, EastLongmeadow, and Francis J. Pokigo, Ludlow, Mass., assignors to MonsantoChemical Company, St. Louis, Mo., a corporation of Delaware NoDrawing.Application February 16, 1949, Serial No. 76,851

4 Claims. 1

This invention relates to a process for coloring vlnylidene polymers andcopolymers. More particularly, the invention relates to a method forcoloring vinylidene polymers and copolymers in aqueous emulsion form.

' One of the best ways for preparing vinylidene polymers and copolymersis to polymerize the monomers in aqueous emulsion in the presence of anemulsifying agent and a suitable polymerization catalyst. Thepolymerized material is colorless and remains emulsified in the aqueousmedium until steps are taken to remove the water therefrom. Incommercial practice, a large amount of the polymers and copolymers thusobtained must be colored since one of the outstanding advantages ofpolymeric materials isthe multitude of colors available therein.

Several ways have been suggested for incorporating color into vinylidenepolymers, most of which require that the polymer be dried and subjectedto a further processing step. It has also been suggested that anoil-soluble organic dye be added to a volatile material which is anonsolvent for the polymer and the dye solution thus formed beincorporated in the aqueous emulsion of the polymer or copolymer. Thisprocess has the advantage that the color may be added to the emulsionand thoroughly dispersed throughout the resin by simple agitating meansbefore the emulsion is resolved and the polymer is obtained in a driedform. However, it has been found that the volatile non-solvent has atendency to upset the balance in the emulsion resulting in prematurecoagulation so that the old step of treating the polymer on hot millingrolls has been necessary to disperse the color. In addition, it has alsobeen found that it is quite difiicult to remove all of the volatilenon-solvent with the result that the polymer obtained therefrom issofter than normal and tends to shrink on standing over long periods oftime.

One object of this invention is to provide a process for coloringvinylidene polymers and copolymers.

A further object is to provide a process for adding color to aqueousemulsions of vinylidene polymers and copolymers. 7

These and other objects are attained by dis: solving an oil-solubleorganic dyestuff in an allphatic acid containing from 6 to 20 carbonatoms, adding an amine to the dye solution thus obtained, emulsifyingthe product in water and adding the emulsion thus obtained to an aqueousemulsion of a vinylidene polymer or copolymer.

The following examples are given in illustration zen-23.5)

and are not intended as limitations on the scope of this invention.Where parts are mentioned, they are parts by weight.

No. 258) in stearic acid was prepared by heating 30 parts of stearicacid until it was in liquid form and then adding 1 part of CondensationRed to the molten acid with constant agitation. After all of the colorwas dissolved, 15.0 parts of triethanol amine were added to the hotsolution. To this mixture 500 parts of water, which had been preheatedto about 180 F., was added slowly with constant agitation until anemulsion of the color in water was obtained.

The emulsion of the Condensation Red was then added to an aqueousemulsion of polystyrene in the ratio of 2 parts of color emulsion toparts of polystyrene emulsion. The mixture was agitated until the coloremulsion was thoroughly dispersed throughout the polystyrene emulsion.The colored polystyrene emulsion was then agitated at high speeds atroom temperature until coagulation occurred. Coagulation was firstobserved after 64 minutes which compares favorably with an uncoloredpolystyrene emulsion which coagulated after 66 minutes.

The product was a thick paste of colored polystyrene in water. The waterwas removed from the paste by drying it in an oven at about 100 C. Thedried powder was easily molded by injection or compression moldingmethods and yielded articles which were uniformly colored and had thesame hardness and dimensional stability as uncolored polystyrene.

The polystyrene emulsion used in the example was prepared bypolymerizing styrene monomer in an aqueous medium containing a sodiumsalt of mahogany acids as emulsifier and ammonium persulfate as acatalyst. The final emulsion contained about40% solids by weight.

When attempts were made to color the same polystyrene emulsion withsolutions of Condensation Red in acetone and in dioxane, both of whichare volatile non-solvents for polystyrene, the colored emulsionscoagulated in a much shorter time, i. e., 40 minutes for the acetonesolution and 37 minutes for the dioxane solution.

Both of the coagulated emulsions were dried in ovens at about 100 C. andthen molded by injection molding methods. The color of the moldedobjects was not uniform and the objects shrank on aging. The objectsmade from the colored polystyrene in which dioxane was used 3 as asolvent for the dye were noticeably softer than normal polystyrene.

Example II In this example an aqueous emulsion of a copolymer ofpolystyrene and alpha methyl styrene (95% styrene) containing 40% solidsby weight was colored by the addition thereto of an emulsion of OilYellow OB (Color Index No. 61). The coagulation time 01 the coloredemulsion was substantially the same as that of the uncolored emulsion.The dye emulsion was made by dissolving 2 parts of Oil Yellow B in 30parts of oleic acid, adding 14 parts of octylamine and emulsifying themixture in 500' parts of water. 2 parts of the color emulsion was usedto color 100 parts of the copolymer emu sion.

Example HI An aqueous emulsion of a copolymer of vinyl chloride anddiethyl maleam (90% vinyl chloride by weight) was colored with anemulsion prepared by dissolving 4 parts of Fast Orange A (Color Index24) in 30 parts of palmitic acid at a temperature at which the acid isin the liquid state, adding 16 parts of diethanolamine to the solutionand then adding hot water to the mixture with constant agitation untilan emulsion was formed. 6 parts of the color emulsion were added to 100parts of the vinyl chloridediethyl maleate copolymer emulsion. Thecolored copolymer emulsion had substantially the same coagulation timeas the uncolored copolymer emulsion.

Each of the colored polymer of copolymer emulsions of the examples wasdried on drum driers and the dry resin thus obtained was molded ininjection molding machines under conventional conditions. The moldedobjects were uniform in color throughout with no highly colored oruncolored spots observable-in any of the individual molded pieces.

The process of this invention may also be used to color polymer andcopolymer emulsions which are to be used for coating and adhesivepurposes. For such uses the final emulsions are quite stable tocoagulation and are substantially unaffected in this respect by theaddition of the dye emulsion. Films and coatings prepared from thestable emulsions colored by the process of this invention show a uniformcoloration without the presence of color specks or uncolored portions.

Example IV A 40% solids polystyrene emulsion was prepared bypolymerizing styrene in an aqueous medium in the presence of ammoniumoleate and the sodium salt of a styrene-maleic anhydride copolymer asemulsifying agents and ammonium persulfate as the polymerizationcatalyst. The resultant emulsion was stable to coagulation over a periodof weeks and could be used to coat a film of polystyrene on wood, metaland other surfaces. To 100 parts of this emulsion, there were addedparts of the color emulsion prepared as shown in Example I. The coloredpolystyrene emulsion thus obtained had substantially the same stabilityas the uncolored emulsions and films coated onto wood or metal surfacesshowed an even, homogeneous coloring.

The resins which may be colored by the process of this invention arepolymers and copolymers of vinylidene compounds which may be polymerizedin aqueous emulsion, i. e., compounds which are substantially insolublein water. The process may also be applied to vinylidene polymers andcopolymers made by methods other than the aqueous emulsionpolymerization process provided that the resins are subsequentlyemulsified in water. Resins which may be colored by the process of thisinvention are polymers and copolymers of: vinyl esters including vinylacetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyllaurate, vinyl stearate, vinyl benzoate, vinyl Iuroate, etc.; vinylethers such as vinyl methyl ether, vinyl ethyl ether, vinyl propylether, vinyl butyl ether, vinyl phenyl ether, divinyl ether, etc.; vinylhalides including vinyl chloride, vinyl fluoride, vinyl bromide andvinyl iodide; vinyl amides and imides such as N-vinyl phthalimide,N-vinyl adlpamide, N-vinyl succinimide, vinyl carbazole, etc; acrylicand q-substituted acrylic acids and their derivatives including esters,amides and nitriles thereof such as acrylic, methacrylic, ethacrylic,phenylacrylic acids, and the corresponding nitriles, anrylamide,methacrylamide, phenylacrylamide and their N- substituted derivativessuch as N-methyl acrylamide, N,N-diethyl methacrylamide, and the methyl,ethyl, butyl, phenyl, cyclohexyl, etc. esters of acrylic, methacrylic,ethacrylic, phenylacrylic, etc. acids; allyl compounds corresponding tothevinyl compounds including allyl alcohol, allyl esters, allyl acetate,allyl caproate, allyl ethers, allyl ethyl ether, allyl butyl ether,diallyl ether, allyl vinyl ether, allyl halides, allyl chloride, allylfluoride, etc. unsaturated polymerizable hydrocarbons such as butadiene,isoprene, piperylene, ethylene, proplyene, isobutylene, styrene,ring-substituted styrenes, o-, m-, or pchloro-styrenes, o-, m-, orp-methyl, ethyl or butyl styrenes, 2,5-dichlorostyrene,2,5-difluorostyrene, o,p-dimethyl styrene, side-chain sub stitutedstyrenes, a-methyl styrene, a-propyl styrene, a-phenyl styrene,a-methyl-p-methyl styrene, vinyl naphthalene, divinyl benzene, etc.polymerizable a, 8- unsaturated polybasic acids and their derivativessuch as maleic citraconic, fumaric, itaconic, etc., acids and theiresters and amides inluding the monoand di-methyl, ethyl, butyl, phenyl,etc. esters, maleic acid amide, itaconic acid amide, N-methyl maleicacid amide, N,N-diethy1 itaconic acid amide, etc. Polyvinyl acetals andketals which are not made by an emulsion polymerization process may beemulsifled in water and then colored by the process of this invention.

The colors which may be used to modify the resin emulsions areoil-soluble organic dyes which are soluble in aliphatic acids containing6-20 carbon atoms. Exemplary of the dyes which may be used are:aniline-azo-naphthyl amine yellow (C. I. 22) Fast Orange A (C. I. 24),Oil Scarlet LB (C. I. 248), Sudan Red IV also known as Condensation Red(C. I. 258), Brilliant Fast Brown B, Spirit Yellow R (C. I. 17), OilYellow OB (C. I. 61), and many others, the

' names and nature of which may be easily ascerdyes but also areimportant aids to the emu1siflcation thereof. Among the preferred acidsare; stearic, palmitic, oleic, linoleic, linolenic. palmitolic, elaidic,pentadecylic, margaric, etc., acids. Many of the preferred acids aresolids at room temperatures and should be heated to above their meltingpoints to readily dissolve the dyes. In such an event the water used asthe emulsifying medium should also be heated to a point above themelting point of the acid until the emulsification is completed.

After the dye has been dissolved in the acid, at least a portion andpreferably all oi the acid should be neutralized with an amine.Aliphatic monoamines including the aliphatic alcohol amines are thepreferred neutralizing agents with the added restriction that theyshould be substantially non-volatile at the temperatures used incarrying out this invention, i. e., up to about 150 0. Among the amineswhich may be used are mono, di-, and triethanol amines, and thecorresponding butanol amines, mono-, diand trialkyl amines containing atleast 4 carbon atoms in the alkyl group such as the butyl amines, amylamines, hexylamines, octyl amines, decyl amines, octadecyl amines, etc;A mixture of amines may be used.

The amount of dye to be incorporated in the acids will depend on thestrength and solubility thereof and to some extent on the color desiredin the finished product although the latter limitation is more afunction of the amount of color emulsion which is added to the resinemulsion. For eflicient coloring action, from 1 to parts oi oil-solubledye will be dissolved in 100 parts of the acids.

The amount of amine used may be varied between 0.1 to 1.5 mols per molof acid. Usually, it will be found convenient to add from 0.5 to 1.0 molof amine per mol of acid.

The amount of color emulsion added to the resin emulsion may be variedsubstantially depending on the strength of the dye, the amount of dye inthe color emulsion, etc. Since the process is applicable to theproduction otvery light tints as well as highely colored materials, theamount of the color emulsion used is not critical.

Number However, for economic reasons it is desirable to prepare thecolor emulsion in concentrated form and to use igrom 1 to 10 parts ofcolor emulsion per parts of resin emulsion.

The 'process of this invention is especially valuable in the colorationof emulsions of vinylidene polymers and copolymers since it provides amethod for obtaining uniform and homogeneous colored resins which may beused in injection molding processes, film casting processes or incoating processes. The invention eliminates the tedious and oftendiflicult steps of adding color to the resins in lBanbury mixers, on hotmilling rolls or by other conventional means of adding color to theresins.

It is obvious that many variations may be made in the products andprocesses of this invention without departing from the spirit and scopethereof as defined in the appended claims.

What is claimed is:

l. A process for the coloration of vinylidene polymers which comprisesadding to an aqueous emulsion of a vinylidene polymer an emulusion of anoil-soluble organic dye, said dye emulsion having been produced bydissolving the dye in a non-volatile aliphatic acid containing from 6 to20 carbon atoms, adding to the solution thus formed from 0.1 to 1.5 molsof a non-volatile aliphatic monoamine per mol of acid and thenemulsifying the mixture with water.

2. A process as in claim 1 wherein the acid contains from 15 to 18carbon atoms.

3. A process as in claim 1 wherein the acid i stearic acid. V

i. A process as in claim 1 wherein the acid is stearic acid and theamine is triethanolamine.

HAROLD F. PARK. FRANCIS J. POKIGO.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PA'I'ENTS Name Date Teague Feb. 21, 1928

1. A PROCESS FOR THE COLORATION OF VINYLIDENE POLYMERS WHICH COMPRISESADDING TO AN AQUEOUS EMULSION OF A VINYLIDENCE POLYMER AN EMULSION OF ANOIL-SOLUBLE ORGANIC DYE, SAID DYE EMULSION HAVING BEEN PRODUCED BYDISSOLVING THE DYE IN A NON-VOLATILE ALIPHATIC ACID CONTAINING FROM 6 TO20 CARBON ATOMS, ADDING TO THE SOLUTION THUS FORMED FROM 0.1 TO 1.5 MOLSOF A NON-VOLATILE ALIPHATIC MONOAMINE PER MOL OF ACID AND THENEMULSIFYING THE MIXTURE WITH WATER.